1. Field of Invention
This invention relates generally to valve box locking lids for and, more specifically; to a valve box locking lid providing both a secure fit and improved debris protection.
2. Background of the Invention
Municipal utilities typically bury their mains under public rights of way, such as streets, at spaced intervals throughout the system. Normally, open shut-off valves are incorporated for the purpose of isolating main breaks so they can be repaired, or so new connections can be established.
The shut-off valves are frequently buried several feet beneath the street, and access pipes are provided which extend upwardly from the valve to near street level, ending in a valve box. The access pipe provides a passage for a tool which can be manipulated from street level to actuate the valve.
A cover assembly with a removable lid is usually incorporated in the pavement to cover the opening to the valve box, and possibly also to prevent debris from entering the access pipe. It has been customary to fabricate the cover assembly from cast iron. Cast iron has the advantages of being inexpensive and durable. Iron castings, however, are notorious for dimensional variations from one casting to the next. Consequently, it frequently is the case that there is a poor fit between the cover assembly and valve boxxe2x80x94with the result that cover assemblies can become dislodged, creating a potential hazard.
Nevertheless, cast iron has remained the material of choice because it is strong and capable of withstanding the rigors to which a pavement-mounted assembly is subjected. It has more recently been recognized that quality cover assembly components can be modeled from light-weight synthetic polymeric material. U.S. Pat. No. 4,048,766, granted Sep. 20, 1977, to P. H. Dantzer et al. for xe2x80x9cClosure Lid Assembly for Protective Housingsxe2x80x9d suggests the components be formed by a structural foam molding process. The light weight of the lid in the Dantzer et al. assembly requires that special retaining means and a locking system be provided in the design to prevent the lid from being accidentally dislodged. There continues to be a need for an access cover assembly which can be easily molded from polymeric material and which will perform reliably in servicexe2x80x94providing both a secure fit (i.e., resisting dislodging), able to be removed in a convenient manner, and also preventing debris from entering the access pipe. The present invention satisfies these needs and provides other, related, advantages.
It is an object of the present invention to provide a light-weight valve box locking lid that provides a secure fit that will resist accidental dislodging.
It is a further object of the present invention to provide a light-weight valve box locking lid that provides a secure fit that will resist accidental dislodging and that further provides improved debris prevention.
It is yet a further object of the present invention to provide a light-weight valve box locking lid for an access pipe that may be removed in a convenient manner.